1. Field of the Invention
The invention concerns a cosmetic composition including a C.sub.2 -C.sub.28 .alpha.-hydroxy carboxylic acid present in a non-irritating carrier.
2. The Related Art
A soft, supple and flexible skin has a marked cosmetic appeal and is an attribute of normal functioning epidermis. As human skin ages with advancing years, the epidermis can become folded, ridged or furrowed to form wrinkles. These signal of loss of youthful appearance and herald the transition to old age. Exposure to excessive doses of sunlight accelerates the transition process. Also, the outer layer of the epidermis known as the stratum corneum can become dry and flaky following exposure to cold weather or excessive contact with detergents or solvents. Loss of skin moisture thereby results and the skin begins to lose the soft, supple and flexible characteristics.
Emollients such as fats, phospholipids and sterols have in the past been used to soften wrinkled or dry skin. These emollients are only partially effective as a remedy for skin in poor condition.
The use of .alpha.-hydroxy carboxylic acids for enhancing the quality of human skin has been known for some time. There is no doubt that .alpha.-hydroxy carboxylic acids are therapeutically effective much beyond the common emollients.
U.S. Pat. No. 4,424,234 (Alderson et al.) discloses skin treatment compositions incorporating .alpha.-hydroxycaproic acid and .alpha.-hydroxycaprylic acid or mixtures thereof in compositions that have a pH value of less than 7, usually from 2 to 4. Yu and Van Scott have patented widely in this area. For instance, U.S. Pat. No. 4,105,782 reports amines or ammonium salts of .alpha.-hydroxy carboxylic acids in the treatment of acne or dandruff. In U.S. Pat. No. 4,105,783 and U.S. Pat. No. 4,197,316, these compounds are suggested for the treatment of dry skin. U.S. Pat. No. 4,234,599 discloses the use of .alpha.-hydroxy carboxylic acids, their esters or amine salts in the treatment of keratoses. More recently, U.S. Pat. No. 5,091,171 focused attention on these compounds as being effective against age spots, wrinkles and aging relative skin changes.
While .alpha.-hydroxy carboxylic acids hold much therapeutic promise, these materials have been found to irritate human skin on repeated topical applications. The irritation may range from a sensation of tingling, itching and burning to clinical signs of redness and peeling. Causes for such irritation have been linked to the lowering of pH in the stratum corneum of human skin. Low pH has been suggested as provoking disturbances in intercorneocyte bondings resulting in adverse skin reactions, specially in some individuals with sensitive skin.
Accordingly, it is an object of the present invention to provide a composition including .alpha.-hydroxy carboxylic acids with a carrier formulation that avoids irritation including the sensation of tingling, itching and burning as well as any clinical signs of redness and peeling.
This object and others will become more evident through consideration of the following summary, detailed description and examples which follow.